Lymphatic System
Chapter 22 - BIO 100
–Lymphatic system
•Functions
–Return excess tissue fluid to bloodstream
–Defense against disease
•Lymphatic vessels – a one-way system
–Begins with capillaries in tissues
–Fluid inside is lymph
»Water, nutrients, electrolytes
»Cell products like hormones
•Lymphatic vessels
–Lymphatic capillaries merge to form vessels
–Vessels merge and empty into ducts
•Thoracic duct-empties
•Vesselstructure
–Small and larage vessels
•Similar to veins, with valves to prevent backflow
•Skeletal muscles “pump” lymph
•Edema
–Accumulation of tissue fluid
–Occurs if not enough drainage, or too much produced
–Can cause tissue damage and death
•Lymphatic organs
–Contain lymphocytes
•Produced in thymus and bone marrow
•Antibodies (B Lymphocytes)
•Cellular immunity (T lymphocytes)
–Primary lymphatic organs
•Red bone marrow where stem cells produce blood cells
•The Primary lymphatic organs include:
–The Thymus
•Between trachea and sternum above the heart
•Shrinks with age
•Divided into 2 lobules
•Produces hormones – Thymosin
•The Secondary lymphatic organs include
–The Spleen - upper left side of abdomen
•Lymph nodes
•Located along lymphatic vessels
•Nodules connective tissue & packed with B and T lymphocytes
•Lymph filters through nodules
–Macrophages phagocytize pathogens and debris
•Lymph nodes named for location
–Inguinal nodes - groin
–Axillary nodes - armpit
–Cervical nodes - neck
Defense Barriers
•Skin
–Most organism don survive well
–Lack the needed water & nutrients
–Presence of oil and sweat –
•Contain lactic acid that inhibits bacterial/fungal growth
–Shedding of skin
•Mucous memebranes
–Harbor bacteria but possess effective defenses
–Contain antibacterial enzymes
–Traps debris & organisms that enter mouth or nose
–Cilia sweep mucus and microbes out of the body
–Expelled via coughing, sneezing or swallowing
Nonspecific specific defenses
•Inflammatory reaction
•Initiated by chemical agents or pathogens
•The 4 classic signs: Redness, Heat, Swelling, Pain
–Signs due to capillary changes – release of Histamine
•Inflammatory Response
–Army of phagocyte (natural killers) to destroy microbes by engulfing or digesting them
•Neutrophils, Monocytes (blood)
•Dendritic cells (skin)
•Macrophages (tissues)
–Isolate the infection
–Fever – slows down microbe production
–Inflammation – released histamines from damaged cells.
•Inflammatory Response
–Phagocytes enfulf microbes, debris, damaged cells
–Each phagocyte can only eat few microbes and then it dies.
–In severe tissue damage or wounds, the surrounding fluid will turn into pus.
–Pus- dead phagocytes and debris
–Fever – macrophages release chemicals into the bloodstream
•Hypothalamus of the brain raises the thermostat
•Active immunity
•Response to vaccination
•Monitored by antibody titre
•After first exposure, one gets primary response
•Booster response
–Boosts the titre to high level
•Active immunity depends on memory T and B cells
•Passive immunity
–Comes from prepared antibodies
–Not produced by individual’s body
–Temporary immunity used to prevent illness
Immunity side effects
•Allergies
–Hypersensitivities to allergens
–Immediate allergic response
•occurs within seconds
•Hay fever- reaction in mucous membranes of nose/eyes
•Asthma- reaction occurs in small airways
•Anaphylactic shock
–Allergen enters bloodstream
–Life-threatening
–Epinephrine can delay reaction
•Antigens – the invader
–large complex molecules that are recognize as foreign body
•Antibodies – the army, interact with the antigens
–Are produce by B-cells and T-cells
•Blood-type reactions
–ABO system
•Based on presence or absence of A and B antigens on RBC’s
–If A present- blood is type A
–If B present- blood is type B
–If both resent- blood is type AB
–If neither is present- blood is type O
–Transfusions
•Must consider recipient’s antibodies and donor’s antigens to prevent agglutination and transfusion reaction
•Type O is universal donor
–Neither anti-A nor anti-B antibodies
•Type AB is universal recipient
–Neither A nor B antigens
Blood-type reactions
Rh system
–Antigen present- Rh positive
–Antigen absent- Rh negative
•Significant in pregnancy
–Rh neg mom pregnant with Rh pos baby
–If baby’s cells leak into mother’s bloodstream, she forms anti-Rh antibodies
»Attack baby’s RBC’s- hemolytic disease of newborn
»Can affect subsequent Rh pos pregnancies
–Pevent by giving Rh neg mom anti-Rh immunoglobulins in an injection
Diseases of the immune system
–Autoimmune diseases
•Cytotoxic T cells or antibodies attack body’s cells
•No cures available; it is only controlled with drugs
Examples:
1.Myasthenia gravis - neuromuscular junctions do not work
2.Multiple sclerosis -myelin sheath of neurons break down
3.Systemic lupus erythematosis - many systemic signs
4.Rheumatoid arthritis - affects joints
•Immunodeficiency diseases
•Immune system unable to protect against disease
•Can be congenital from defect in lymphocyte formation
•Can be infectious- HIV
•Severe combined immunodeficiency disease-both T cells and B cells affected